1. 1 Copyright Ken Fletcher 2004 Australian Computer Security Pty Ltd Printed 25-Nov-15 15:40 Prepared for: Monash University Subj: CSE4884 Network Design & Management CSE4884 Network Design and Management Lecturer: Ken Fletcher Tutorial Network Traffic Analysis Background and Examples

2. 2 Copyright Ken Fletcher 2004 Australian Computer Security Pty Ltd Printed 25-Nov-15 15:40 Prepared for: Monash University Subj: CSE4884 Network Design & Management Network Traffic Analysis n The fundamental need in design work is quantification of requirements. EG Nobody would design an aircraft without consideration of –required carrying capacity, flying range, operating height n Similarly with communications networks - we need to know the basic traffic loads to be used as the basis for ‘design load’ n Strange as it may seem, you will spend more time determining and analysing traffic loads than actually ‘designing’ the network. n In the end you will be fortunate if you can determine the design traffic loads within 50% to 100% of those that will actually occur on the new network.

3. 3 Copyright Ken Fletcher 2004 Australian Computer Security Pty Ltd Printed 25-Nov-15 15:40 Prepared for: Monash University Subj: CSE4884 Network Design & Management Customer Furnished Information (CFI) n Despite best intentions the customer or client can rarely give you the traffic figures in the form you need –The designer works with the future in mind, and needs figures which user management has not had to worry about yet - and have neither collected nor even thought about such matters –Customer management have historical figures available, and estimates of the future (management have reliable past figures available, rather than future figures) –Customer management have limited understanding of technical issues, and hence cannot immediately give the type of figures wanted eg distribution of transaction sizes –Usually the customer has figures which have been meaningful to them, and you must start with these You must work with the figures available from the customer, and re- structure these into the forms you need.

4. 4 Copyright Ken Fletcher 2004 Australian Computer Security Pty Ltd Printed 25-Nov-15 15:40 Prepared for: Monash University Subj: CSE4884 Network Design & Management Exercise 1 n Traffic flows (messages) –0800-090010 per min –0900-100020 per min –1000-110030 per min –1100-120040 per min –1200-130030 per min –1300-140020 per min –1400-150010 per min n Q1.1 What is the average traffic flow rate? ………messages per …. n Q1.2 What figures would you use for network design, and why? Describe: ……………………………………………………… Values: ………… …………… per ……….

5. 5 Copyright Ken Fletcher 2004 Australian Computer Security Pty Ltd Printed 25-Nov-15 15:40 Prepared for: Monash University Subj: CSE4884 Network Design & Management Exercise 2 n There are ‘n’ terminals at a call-centre site Each terminal averages 1 transaction per minute during peak periods (eg from 16:00 to 17:00 daily M-F) Each computer transaction is 1000 characters Packet overheads are 10% –ie 100 application characters results in 110 characters being transmitted A character requires 8 data bits Bearer is asynchronous (one start bit, one stop bit per data character) n Q2.1 n How many bits in a character? Application: …….. Transmission:………. n Q2.2 n How many characters in a transaction? Application:……. Transmission:……. n Q2.3 Derive an expression for the average Tx traffic load in peak periods

6. 6 Copyright Ken Fletcher 2004 Australian Computer Security Pty Ltd Printed 25-Nov-15 15:40 Prepared for: Monash University Subj: CSE4884 Network Design & Management Exercise 2 (Continued) n Q2.4 What is the traffic load: Q2.4a.………. …………….per hour OR Q2.4b ……….. …………….per minute OR Q2.4c.………. …………….per second n Q2.5 Consider that a transaction must be processed within 2 seconds: Q2.5 a. Which of the figures from Q2.4 are meaningful? ……………………………………………………………………... Q2.5 b. What figure should be used for design (give reasons)? ………………………………………………………………………..

7. 7 Copyright Ken Fletcher 2004 Australian Computer Security Pty Ltd Printed 25-Nov-15 15:40 Prepared for: Monash University Subj: CSE4884 Network Design & Management Exercise 3 n The following traffic is to be carried from Site A to Site B TypeVolumePeriodWhen? Backup1000MB2 hoursovernight Voice8*64kbps0900-1000 daily Voice6*64kbps1200-1600 daily Telemetry10kbps inbound24x7 Video conference facility 384kbps each waywhen required emails100MB per day each way“when they arrive” Q3.1 What assumptions are you making? Q3.2 What is the maximum load? Q3.3 When does it occur?

8. 8 Copyright Ken Fletcher 2004 Australian Computer Security Pty Ltd Printed 25-Nov-15 15:40 Prepared for: Monash University Subj: CSE4884 Network Design & Management Exercise 4 n A company has regional offices in Melbourne, Sydney, Adelaide and Perth. All data is sent online to the head office in Auckland (NZ) as soon as it is processed at the regional office. n At 1200 in Auckland, it is 0900 Australian Eastern Standard Time (east coast cities), 0830 Australian Central Standard Time and 0700 Australian West Coast Time n Each regional office has a local peak period between 1000 and 1200 hours each working day. n Regional offices range from Sydney (25 staff) to Perth (5 staff) Q4.1 When is the peak time for traffic going to Auckland? Q4.2 What assumptions have you made?

9. 9 Copyright Ken Fletcher 2004 Australian Computer Security Pty Ltd Printed 25-Nov-15 15:40 Prepared for: Monash University Subj: CSE4884 Network Design & Management Lessons to be learned - General n Convert data to similar units throughout your task where possible. This avoids a lot of errors. Communications tend to work with: –clock time in 24 hours style –single time basis for communications involving multiple time zones. On a network with links in different time zones, work using the earliest zone as the basis,or use a Universal Time approach (ie GMT, UMT, or ‘Zulu’ time). Note that this is mainly caused by links oriented east-west. North-south links are normally in the same time zone except during ‘Summer time’ periods when locations within 23 degrees of the equator normally do not go to summer time.. –Data rates are normally used in bits per second (bps) - or multiples such as Kbps, Mbps, Gbps. Note that there is confusion about values of K, M and G ie does K=1000 or is K=1024? –Busy or peak rates of ‘X per second’, ‘X per minute’ or ‘X per hour’ Activity rate is usually used in terms of activity per second, (or minute or hour), but is often specified in other terms. eg “in 5 minutes we received 20 calls” - this is a call rate of 240 calls per hour, or 4 calls per minute.

10. 10 Copyright Ken Fletcher 2004 Australian Computer Security Pty Ltd Printed 25-Nov-15 15:40 Prepared for: Monash University Subj: CSE4884 Network Design & Management Lessons to be learned - Traffic Loads n The customer will give you the best figures that they can - and you must work with these. Inevitably they will be less than perfect. Do not wait for customer data to be perfect - you will not live that long n Generally the most significant figures are those considered as ‘repetitive peak loads’ - where ‘repetitive’ may be daily, weekly, monthly etc depending on the customer’s domain. No network can be built to handle the most extreme situation possible - it must be designed to cope with ‘working’ or repetitive worst case n Often best to take the customers raw figures and work on refining these by determining ‘typical’, ‘peak’ etc loads. Report these back to the customer in writing, with a request for a written confirmation that these are the figures to be used for design work.

11. 11 Copyright Ken Fletcher 2004 Australian Computer Security Pty Ltd Printed 25-Nov-15 15:40 Prepared for: Monash University Subj: CSE4884 Network Design & Management For the third time... n Strange as it may seem, you will spend more time determining and analysing these issues than actually ‘designing’ the network. The ‘dimensioning calculations’ task is usually a fairly quick activity - and is performed with a spreadsheet or calculator n Most newly installed networks shortly experience traffic loads in excess of the design loads - perhaps 50% to 100% or even more. This is caused by several factors - including: poor traffic forecasts; –often a hidden “suppressed-demand” situation a ‘new toy’ which people want to play with the ‘freeway effect’ AKA the ‘turnpike effect’ - (“it is better than the old, so let us use it more than before”)